Field of the Invention
The present invention relates to an image processing apparatus which reconstructs an input image to generate a plurality of output images with different focus positions.
Description of the Related Art
Recently, an image pickup apparatus is provided which outputs various images by performing calculation on data obtained by an image pickup element and performing a digital image process corresponding thereto. Ren Ng, et al., “Light Field Photography with A Hand-held Plenoptic CAMERA”, 2005 COMPUTER Science Technical Report CTSR, and Todor Georgiev, et al., “Superresolution with Plenoptic 2.0 CAMERA”, 2009 Optical Society OF America disclose an image pickup apparatus which simultaneously obtains two-dimensional intensity distribution of light in an object space and angle information of a light beam, that is, parallax information, using “Light Field Photography”. The two-dimensional intensity distribution of light and the angle information of a light beam are collectively called light field, and it is possible to obtain three-dimensional information of the object space by obtaining the light field. By performing a reconstruction process of an image using the obtained light field, it is possible to perform refocusing such as changing a focus position of an image, changing an imaging viewpoint, and adjusting a depth of field.
Meanwhile, the image pickup apparatus is required to have further high image quality according to advance of a display device. For high image quality, it is important to reduce noise of an image. Japanese Patent Laid-open No. H06-86332 discloses a method of reducing noise by combining images obtained through a plurality of image pickup optical systems.
However, in the noise reducing method disclosed in Japanese Patent Laid-Open No. H06-86332, pixels that image the same object are simply combined. In this case, when the noise follows Poisson distribution, N pixels are combined such that the noise is reduced by N−1/2 times by averaging. However, according to the advance of the display device, the image is required to have further high quality, and thus the noise reducing method disclosed in Japanese Patent Laid-Open No. H06-86332 is insufficient.